Solid ink or phase change ink printers conventionally receive ink in a solid form, either as pellets or as ink sticks. The solid ink pellets or ink sticks are placed in a feed chute and a feed mechanism delivers the solid ink to a heater assembly. Solid ink sticks are either gravity fed, belt driven or urged by a spring through the feed chute toward a heater plate in the heater assembly. The heater plate melts the solid ink impinging on the plate into a liquid that is delivered to a print head for jetting onto a recording medium. U.S. Pat. No. 5,734,402 for a Solid Ink Feed System, issued Mar. 31, 1998 to Rousseau et al.; and U.S. Pat. No. 5,861,903 for an Ink Feed System, issued Jan. 19, 1999 to Crawford et al. describe exemplary systems for delivering solid ink sticks into a phase change ink printer.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. A color printer typically uses four colors of ink (yellow, cyan, magenta, and black). These colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. Suitable carrier materials can include paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, fatty acids and other waxy materials, fatty amide containing materials, sulfonamide materials, resinous materials made from different natural sources (tall oil rosins and rosin esters, for example), and many synthetic resins, oligomers, polymers, and copolymers.
One problem faced in solid ink technology is differentiation and identification of ink sticks to ensure the correct loading and compatibility of an ink stick with the imaging device in which it is used. The wrong color of ink stick in a feed channel, ink sticks intended for different solid ink printers, use of non-qualified ink, etc. may impact image quality or even damage the solid ink imaging device. In previously known phase change ink systems, differentiation and identification of ink sticks was accomplished by incorporating keying features into the exterior surface of an ink stick. A corresponding key place of an ink loader acted to exclude inappropriately keyed ink sticks from being inserted into a feed channel of the printer.
World markets with various pricing and color table preferences have created a situation where multiple ink types may exist in the market simultaneously with nearly identical size/shape ink and/or ink packaging. Thus, ink sticks may appear to be substantially the same but, in fact, may be intended for different phase change printing systems due to factors such as, for example, market pricing or color table. Due to the broad range of possible ink stick configurations, marketing strategies, pricing, etc., differentiating the inks sticks so only appropriate ink is accepted by a printer requires methods of identification that go beyond physical keying. Adding conventional labels or tagging mechanisms to an ink stick is not practical, however, because tagging mechanisms may not be compatible with the phase change ink imaging device or the ink composition to which it is applied resulting in contaminated ink, blocked print heads, etc.